Enhanced nitrogen vacancy density induced by sulfur doping on carbon nitride facilitates selective lactic acid production

• A metal-free carbon nitride photocatalyst with NV and S doping was synthesized. • NV and S doping facilitated efficient carrier migration as well as oxygen activation. • S20–CN–NV exhibited exceptional adsorption capacity for glucose. • A 95.5 % of glucose conversion with 95.1 % of LA selectivity was obtained. The integration of biorefining and photocatalysis represents a highly promising approach for enabling the green and efficient synthesis of high-value chemicals derived from biomass. Herein, we successfully synthesized a metal-free carbon nitride photocatalyst doped with sulfur (S), which induced the formation of nitrogen vacancies (N V ). The optimized catalyst (S 20 –CN–N V ) exhibits outstanding photocatalytic activity, achieving 95.5 % of glucose conversion and 95.1 % of lactic acid (LA) selectivity within 60 min under visible-light irradiation. Remarkably, the LA yield remains impressively high at the initial 97.5 % even after 6 cycles. Experimental studies and characterizations reveal that S doping significantly increased the concentration of N V , and the synergistic effect of N V and S doping enhanced the visible-light absorption and facilitated the separation of photogenerated carriers as well as the activation of oxygen, thereby promoting the generation of superoxide radicals. Density functional theory simulations further reveal that S 20 –CN–N V exhibits exceptional glucose adsorption capacity and requires low activation energy in the rate-limiting step. Consequently, S doping induced the formation of N V thus boosted the photocatalytic oxidation process of glucose into LA. This study provides valuable insights for guiding the design of photocatalyst through nonmetal-doping and defect engineering strategies, facilitating the efficient valorization of biomass-derived platform chemicals. Carbon nitride photocatalyst (S 20 –CN–N V ) with enhanced nitrogen vacancy induced by sulfur doping displays excellent photocatalytic activity with lactic acid selectivity of 95.1 %.